What is the difference between kVA and kW?

kW (kilowatts) measures real power, which is the rate at which energy is actually consumed and converted into useful work or heat. kVA (kilovolt-amperes) measures apparent power, which is the product of the RMS voltage and RMS current without regard to the phase angle between them. The ratio kW divided by kVA is the power factor. A purely resistive load such as a heater has a power factor of 1 and kW equals kVA. Inductive loads such as motors and transformers have a power factor less than 1, so they draw more apparent power than they convert into real work.

What is a typical power factor for NZ commercial premises?

Many NZ commercial and industrial electricity tariffs target a power factor of 0.8 to 0.95. A lower power factor means more current is drawn from the network to deliver the same real power, increasing losses and requiring larger cables and switchgear. Vector Metering and some NZ lines companies include power factor penalties or incentives in their pricing. Power factor correction capacitors can raise a poor power factor closer to unity.

What is reactive power kVAR?

Reactive power (kVAR, kilovolt-amperes reactive) is the component of apparent power that does no real work but is necessary to maintain the electric and magnetic fields in inductive and capacitive equipment such as motors, transformers and capacitors. It is related to real power and apparent power by the power triangle: kVA squared equals kW squared plus kVAR squared.

kVA to kW Calculator

This calculator converts between kilovolt-amperes (kVA) and kilowatts (kW) in both directions. Enter either the apparent power (kVA) or the real power (kW), along with the power factor, and the calculator returns all three power quantities: real power in kW, apparent power in kVA, and reactive power in kVAR. Understanding the difference between these quantities is important for correctly sizing generators, UPS systems, transformers, and switchgear in New Zealand commercial and industrial installations. Real power (kW) is the useful power that does actual work, such as running a motor or lighting a building. Apparent power (kVA) is the total power drawn from the supply, including both the real component and the reactive component that circulates back and forth in the network maintaining magnetic and electric fields. The ratio of real to apparent power is the power factor, which ranges from 0 to 1. A power factor of 1 means all the apparent power is being converted to real work. A power factor of 0.85 is a common design target and regulatory threshold for NZ commercial premises. In a three-phase system the same kVA to kW relationship applies: kW = kVA x power factor. The line current for a three-phase load is I = kVA x 1000 / (sqrt(3) x V_line). The NZ standard three-phase supply is 400 V line-to-line (230 V phase-to-neutral). Enter your values below and all outputs update instantly.

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Convert from

Power value

kVA

Power factor

8.5 kW

real power (kW)

Apparent power10 kVA

Reactive power5.27 kVAR

Power factor0.85

Power factor ranges from 0 to 1. Unity (1.0) means all apparent power is real power. Most NZ commercial loads have a power factor between 0.7 and 0.95.

How it works

When converting from kVA: kW = kVA x PF and kVAR = kVA x sqrt(1 minus PF squared). When converting from kW: kVA = kW / PF and kVAR = kVA x sqrt(1 minus PF squared). The power triangle relationship is kVA squared = kW squared + kVAR squared. Power factor must be between 0 and 1; if it is outside this range the calculator shows an error. The power factor angle theta relates the three quantities: kW = kVA x cos(theta) and kVAR = kVA x sin(theta).

Worked example

A generator is rated at 10 kVA with a load power factor of 0.85. The real power delivered is 10 x 0.85 = 8.5 kW. The reactive power is 10 x sqrt(1 minus 0.85 squared) = 10 x sqrt(1 minus 0.7225) = 10 x sqrt(0.2775) = 10 x 0.5268 = 5.27 kVAR. These match the default values above.

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